Distributions of the W1−W2 colour for AllWISE anomalies found in this work (solid black) compared with known sources from AllWISE×SDSS used to train the OCSVM algorithm. Galaxies (1 827 241 objects) are marked by blue dashed lines; stars (298 269 objects) by orange dotted lines; and quasars (141 494 objects) by magenta dot-dashed lines. Vertical lines mark the colour cuts applied to the OCSVM anomaly sample dividing it into four possible subgroups.